Re: [PATCH] powerpc/powernv/prd: Validate whether address to be mapped is part of system RAM

[Vaidyanathan Srinivasan <svaidy@linux.ibm.com>]

* Vasant Hegde <hegdevasant@linux.vnet.ibm.com> [2019-10-02 13:18:56]:

> Add check to validate whether requested page is part of system RAM
> or not before mmap() and error out if its not part of system RAM.
> 
> cat /proc/iomem:
> -----------------
> 00000000-27ffffffff : System RAM
> 2800000000-2fffffffff : namespace0.0
> 200000000000-2027ffffffff : System RAM
> 202800000000-202fffffffff : namespace1.0
> 6000000000000-6003fbfffffff : pciex@600c3c0000000
> 6004000000000-6007f7fffffff : pciex@600c3c0100000
> ....
> ....
> 
> Sample dmesg output with this fix:
> ----------------------------------
> [  160.371911] opal-prd: mmap: Requested page is not part of system RAM (addr : 0x0000202ffcfc0000, size : 0x0000000000570000)
> [  160.665366] opal-prd: mmap: Requested page is not part of system RAM (addr : 0x0000202ffcfc0000, size : 0x0000000000570000)
> [  160.914627] opal-prd: mmap: Requested page is not part of system RAM (addr : 0x0000202ffcfc0000, size : 0x0000000000570000)
> [  161.165253] opal-prd: mmap: Requested page is not part of system RAM (addr : 0x0000202ffcfc0000, size : 0x0000000000570000)
> [  161.414604] opal-prd: mmap: Requested page is not part of system RAM (addr : 0x0000202ffcfc0000, size : 0x0000000000570000)

Thanks Vasant for the patch.  HBRT pages landing in NVDIMM area caused
the opal-prd failure.  Good debug and root-cause.

Thanks to Aneesh for the tip to look into ATT bits of the PTE mapping.

> CC: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> CC: Jeremy Kerr <jk@ozlabs.org>
> CC: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
> Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>

Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.ibm.com>

> ---
>  arch/powerpc/platforms/powernv/opal-prd.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/platforms/powernv/opal-prd.c b/arch/powerpc/platforms/powernv/opal-prd.c
> index 45f4223a790f..0f88752302a2 100644
> --- a/arch/powerpc/platforms/powernv/opal-prd.c
> +++ b/arch/powerpc/platforms/powernv/opal-prd.c
> @@ -3,7 +3,7 @@
>   * OPAL Runtime Diagnostics interface driver
>   * Supported on POWERNV platform
>   *
> - * Copyright IBM Corporation 2015
> + * Copyright IBM Corporation 2015-2019
>   */
> 
>  #define pr_fmt(fmt) "opal-prd: " fmt
> @@ -47,6 +47,20 @@ static bool opal_prd_range_is_valid(uint64_t addr, uint64_t size)
>  	if (addr + size < addr)
>  		return false;
> 
> +	/*
> +	 * Check if region is in system RAM and error out if the address
> +	 * belongs to special devices like NVDIMM. phys_mem_access_prot()
> +	 * routine will change ATT bits to non cachable if page is not in
> +	 * RAM, causing HBRT to not fetch and execute in the mapped memory
> +	 * and fail. Page permissions can be left at default since all
> +	 * firmware component should be in system RAM only.
> +	 */
> +	if (!page_is_ram(addr >> PAGE_SHIFT)) {
> +		pr_warn("mmap: Requested page is not part of system RAM "
> +			"(addr : 0x%016llx, size : 0x%016llx)\n", addr, size);
> +		return false;
> +	}
> +
>  	parent = of_find_node_by_path("/reserved-memory");
>  	if (!parent)
>  		return false;
> -- 
> 2.21.0
>